Apparatus and method of increasing web storage in a dancer

ABSTRACT

An improved web accumulator with two arms where at least one arm is a swinging dancer arm and at least one arm is attached to a sliding carriage. Each arm has a set of rollers attached. A web is threaded alternately between the two sets of rollers. The arms are mechanically connected to move simultaneously towards or away from each other. The arms are initially position at their maximum separation to accumulate a maximum length of web. When web infeed is interrupted while web outfeed or draw persists, the arms are first rotated in towards each other to pay out the stored length of web. As the demand persists and the dancer arm is rotated beyond some predefined position, the sliding carriage begins to slide to a least storage position. As web infeed returns to normal operational speeds, the dancer arm and the sliding carriage are returned to their original position to again accumulate a maximum amount of web.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/563,840, filed 20 Apr. 2004, and entitled “Method of Increasing Web Storage in a Dancer.”

BACKGROUND OF THE INVENTION

The invention disclosed herein relates to a method for increasing the amount of web storage available from a web accumulation dancer system. The invention pertains to an accumulator for accumulating a substantial length of a running web such that if the infeed to the accumulator is stopped or slowed for a short interval the web in storage is paid out continuously to a web-utilizing device so that the device has a constant web supply and thus need not be slowed or stopped. Increased storage is an imperative for successful operation of zero speed splicing at very high machine speeds.

A common use of a web accumulator is where a web is fed from a primary supply wheel and it is necessary to splice the leading edge of the web from a standby supply wheel to the trailing edge of the web from the primary supply wheel in a manner that will not cause interruption of the web supply to a web consuming or utilizing device.

In one known type of accumulator, the swinging dancer arm type, there is a set of spaced apart rollers on a swingable dancer arm cooperating with another set of rollers on an arm that may be stationary or swingable. A web is looped back and forth between the sets of rollers on opposed arms in a serpentine fashion. When the swingable arm is swung away from the other arm a substantial length of web is accumulated. During normal running of the web the arms will be urged to their maximum practical separation from each other to accumulate the maximum length of web. If the infeed web is slowed or stopped for a short time the tension in the web urges the arms to the minimum separation position in order to make the accumulated web available to the machine. After infeed to the accumulator is resumed the arms separate again and return to their original position to accumulate and store another length of web.

In another known type of accumulator, the linear sliding carriage type, there is a set of rollers mounted on a movable carriage which can run linearly toward or away from a set of corresponding rollers which may either be stationary or similarly slidably mounted. During normal operation of the accumulator, the two sets of rollers will be slid to their maximum practical separation to accumulate the maximum amount of web. If the infeed supply to the web accumulator is slowed or stopped, the rollers will be slid toward each other to allow the stored web to be paid out. As the web infeed is returned to regular operational speed the movable rollers slide back toward the original position to accumulate another length of web.

It is well known in the art that the swinging arm dancer type of web accumulator first discussed is efficient in that the friction losses to the web are low. However, the dancer type of accumulator does not store a sufficient length of web. Alternatively, the linear sliding carriage type of accumulator allows more web to be accumulated; however, more frictional losses occur.

The consequences of friction and inertia may be appreciated when it is realized that the web may be running at a very high speed when suddenly, for some reason, such as when making a splice, the infeeding web is stopped or decelerated. This change in web motion will result in a reaction by the components of the accumulator. Most notable of these reactions is the motion imparted to the movable assembly of the accumulator. After the web is slowed or stopped, the web at the infeed can only accelerate as fast as the rollers can accelerate. The force to accelerate the rollers is provided by tension in the web. Minimizing the number of rollers and minimizing the inertia of each roller minimizes the necessary web tension.

Minimization and control of the inertia and friction associated with this reaction is therefore an important desired attribute of such accumulators. There is an important need for a web accumulator which provides the benefits of low friction and minimized inertia, allowing it to handle the most delicate of webs at high speeds without breakage or loss of control.

The invention disclosed herein combines a swinging arm dancer with a linear slide. Thus the invention disclosed herein has the advantage of web storage capability substantially equal to that of a linear accumulation system but with minimized frictional losses.

SUMMARY OF THE INVENTION

The new arrangement combines the best features of both previously known accumulators to gain the advantages of both systems while eliminating the disadvantages of each. The new web accumulator achieves a large amount of web storage for the amount of rollers it utilizes.

In general terms, the preferred new web accumulator includes arms, each arm has a set of rollers attached. A web is threaded alternately between the two sets of rollers. The arms are mechanically connected to move simultaneously towards or away from each other. The arms are initially position at their maximum separation to accumulate a maximum length of web. When web infeed is interrupted while web outfeed or draw persists, the arms are first rotated in towards each other to pay out the stored length of web. As the demand persists and the dancer arm is rotated beyond some predefined position, the sliding carriage begins to slide to a least storage position. As web infeed returns to normal operational speeds, the dancer arm and the sliding carriage are returned to their original position to again accumulate a maximum amount of web.

There are several possible variations to this system, such as vertical or horizontal orientation, one or more swinging dancer arms, and either the dancer arm or the linear arm can be sliding.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of the preferred embodiment of the web accumulator.

FIG. 2 is a side elevational view of the accumulator of FIG. 1.

FIG. 3 is a simplified front elevational view of the preferred embodiment of the accumulator of the present invention with its roller carrying arms in the position in which the maximum length of web is accumulated.

FIG. 4 is a similar to FIG. 3 except that the dancer arms of the accumulator are rotating toward each other as would be the case when infeed of the web is stopped and the length of web that is stored in the accumulator is being paid out.

FIG. 5 is similar to FIG. 4 except that the dancer arms of the accumulator have begun to slide toward each other to further pay out the stored web material.

FIG. 6 is similar to FIG. 5 except that the dancer arms of the accumulator have slid to the least storage position.

FIG. 7 is a simplified front elevational view of an alternate embodiment of the accumulator of the present invention with its roller carrying arms in the position in which the maximum length of web is accumulated.

FIG. 8 is similar to FIG. 7 except that the swinging dancer arm of the accumulator is rotating toward the nonrotating linear arm as would be the case when infeed of the web is stopped and the length of web which is stored in the accumulator is being paid out.

FIG. 9 is similar to FIG. 8 except that the nonrotating linear arm has begun to slide toward the rotating arm to further pay out the stored web material.

FIG. 10 is similar to FIG. 9 except that the arms of the accumulator are in the least storage position.

FIG. 11 is a front elevational view of an alternate embodiment of the web accumulator.

FIG. 12 is simplified front elevational view of the accumulator of FIG. 11 with its roller carrying dancer arms in the position in which the maximum length of web is accumulated.

FIG. 13 is a similar to FIG. 12 except that the dancer arms of the accumulator are rotating toward each other as would be the case when infeed of the web is stopped and the length of web that is stored in the accumulator is being paid out.

FIG. 14 is similar to FIG. 13 except that the dancer arms of the accumulator have begun to slide toward each other to further pay out the stored web material.

FIG. 15 is similar to FIG. 14 except that the dancer arms of the accumulator have slid to the least storage position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention.

FIG. 1 illustrates the preferred embodiment of the new web accumulator 20. The accumulator 20 consists of a first swinging dancer arm 22 rotatably mounted to a first carriage 24. First dancer arm 22 rotates about axle shaft 26. A first pneumatic actuator 28 is attached to both first carriage 24 and first dancer arm 22 such that the actuator 28 will function to rotate the dancer arm 22 about axle shaft 26. Dancer arm 22 supports a first set of web accumulator rollers 30 which are individually numbered 30A-30F, inclusive (see, e.g., FIG. 3.) The web accumulation rollers 30A-30F, inclusive, are rotatably mounted on the dancer arm 22. The carriage 24 is slidably mounted on an upper track 32 and a lower track 34.

On the opposite end of the tracks 32 and 34 is a second swinging dancer arm 36 which is preferably identical to first swinging dancer arm 22, but rotated 180 degrees from the first swinging dancer arm 22. Second dancer arm 36 is rotatably mounted to a second carriage 38 for rotation about second axle shaft 40. A second pneumatic actuator is attached to the second dancer arm 36 and the second carriage 38 to facilitate rotation of the second dancer arm 36 about the second axle shaft 40. The second carriage 38 is slidably mounted to the upper track 32 and the lower track 34. A second set of web accumulator rollers 44 which are individually numbered as 44A-44E (see FIG. 2), inclusive are rotatably mounted on the second dancer arm 36.

The drive system includes two idler arms 46 and 48 with flexible mechanical linkage 50. In the preferred embodiment of this invention, the flexible mechanical linkage is a toothed belt. Slidable carriages 24 and 38 are affixed to the belt such that they will not move independently of each other and can only move simultaneously in opposite directions. Carriages 24 and 38 are attached to the toothed belt by clamps 52 and 54, respectively. The drive system is driven by servomotor 56.

It will be noted that in the illustrated embodiment the roller set 30 includes six (6) individual rollers and the roller set 44 includes five (5) rollers. This number can be varied using either a lesser or greater number of rollers as selected for a particular application. However, it will be obvious to one of skill in the art that in order to loop the web between the arms and practice the invention as described herein, the first roller set 30 should include at least two individual rollers and the second roller set 44 should include at least one individual roller. The sets of rollers 30 and 44 are common in the art and therefore are of known configuration.

In FIG. 1 the accumulator 20 is in its maximum storage position as would be the case when the web 60 is being drawn out of the accumulator 20 and is being fed into the accumulator 20 at the same rate. The dancer arms 22 and 36 are swung apart as far as is practical to store the maximum amount of web 60 in the form of loops running back and forth between the dancer arms 22 and 36.

The web 60 is fed into the web accumulator 20. The web 60 first passes around an idler roll assembly 58 which is mounted on the second carriage 38. The web 60 then passes around the first roller 30A of roller set 30 mounted on first dancer arm 22 and next around the first roller 44A of the roller set 44 mounted on second dancer arm 36. The web 60 continues to alternate between the consecutive rollers of roller set 30 and roller set 44 until the web 60 has passed over all the rollers. The web 60 then exits the accumulator 20 and is fed to a web utilization device (not shown).

FIG. 2 is a side elevation view of the accumulator 20 of FIG. 1. This view shows how the individual rollers 44A-44E of roller set 44 are rotationally mounted to dancer arm 36. This view also shows how the dancer arm 36 is attached to the second axle shaft 40 and to the second actuator 42. Servomotor 56 is shown with idler arm 48 shown in phantom lines.

Referring now to FIGS. 3, 4, 5, and 6, the dancer arms 22 and 36 are shown rotating and driven towards each other to pay out accumulated web 60 to the outfeed when infeed of web 60 is stopped for a short interval. FIG. 3 shows the web accumulator 20 in the maximum storage position. FIG. 4 shows the dancer arms 22 and 26 as they are swinging towards each other. The dancer arms 22 and 36 swing towards each other until some specified point when, as shown in FIG. 5, the carriages 24 and 38 on which the dancer arms 22 and 36 are mounted begin to slide toward each other to further continue pay out. FIG. 6 shows the web accumulator 20 in its least storage position, which is the position at which the dancer arms 22 and 26 are the closest.

More specifically, the control of the sliding carriages 24 and 38 is dependent on the displacement of the dancer arms 22 and 36. As the web infeed is slowed or stopped, the tension due to drawing the web 60 from the outfeed end of the web accumulator 20 causes the dancer arms 22 and 36 to move towards the less storage position while the length of web 60 in storage is paid out. The web tension causes the dancer arms 22 and 36 to begin to move. However, the actuators 28 and 42 help drive the swinging dancer arms 22 and 36 to overcome the inertia and friction losses of the roller sets 30 and 44 and dancer arms 22 and 36. If the dancer arms 22 and 36 and roller sets 30 and 44 had no inertia or frictional losses, the force applied to the dancer arms 22 and 36 by the web tension forces would be sufficient to rotate the dancer arms 22 and 36 to the appropriate positions to pay out the stored web. However, because friction and inertia are a factor, the actuators 28 and 42 must drive the rotating dancer arms 22 and 36 to overcome the losses from friction and inertia.

When the dancer arms 22 and 36 reach some predetermined position, the carriage slide drive 56 is commanded to move the carriages 24 and 38 towards each other. Under normal circumstances the carriages 24 and 38 maintain their preset position. In this manner nominal changes in dancer arm 22 and 36 positions are ignored.

As discussed above, the carriages 24 and 38 are mechanically coupled to each other through the drive belt 50 such that they move away from or towards each other synchronously. The velocity of the carriages 24 and 38 is proportional to the rate of displacement of the dancer arms 22 and 36. This allows the system to pay out web 60 such that the web utilizing device is not slowed or stopped. The servomotor 56 is given the command to move the sliding carriages 24 and 38 to the least storage position at a velocity proportional to the displacement error of the dancer arm 22 and 36 position.

As the displacement error is nullified, the carriage slide drive 56 is slowed to a stop even if it has not reached its final commanded position. If the error goes negative, the carriage slide drive 56 is commanded to return the sliding carriages 24 and 38 to the preset position at a velocity proportional to the dancer arm 22 and 36 error.

FIGS. 7, 8, 9, and 10 depict the operation of an alternate embodiment of the web accumulator of the present invention. The alternate embodiment shown in FIG. 7 consists of a first linear arm 122 with a set of rollers 130 rotatably mounted thereon. The linear arm 122 is nonrotatably attached to a carriage 124. The carriage 124 is slidably mounted on a set of tracks (not shown). The carriage 124 is mounted in a known fashion, as described regarding the preferred embodiment above. At the other side of the web accumulator 120 of FIG. 7 is a swinging dancer arm 136 mounted to a plate 138. The dancer arm 136 has a set of rollers 144 rotatably attached thereon.

FIG. 7 shows this alternate embodiment of the accumulator 120 in its maximum web storage position. When the infeed to the accumulator stops or slows, the dancer arm 136 swings toward the linear arm as shown in FIG. 8. When the dancer arm 136 rotates past some predetermined point, the carriage 124 upon which linear arm 122 is mounted begins to slide toward dancer arm 136 as can be seen in FIG. 9. FIG. 10 shows this alternate embodiment of the accumulator 120 in its least storage position.

Another alternate embodiment of the invention (not shown) has one swinging dancer arm and one linear arm, as described above in FIG. 7. However, in this embodiment the swinging dancer arm is slidably mounted on tracks while the linear arm is stationary. When the web infeed slows or stops, the web will pull the swinging dancer arm toward the stationary linear arm. At some predetermined point the dancer arm will be slid toward the stationary linear arm to pay out the remaining accumulated web.

FIGS. 11-15 illustrate yet another alternate embodiment of the web accumulator 220 of the present invention. This embodiment is similar to the preferred embodiment of the invention, however in this embodiment the first swinging dancer arm 222 and the second swinging dancer arm 236 are mirror images of each other. As shown in FIG. 11, the web accumulator 220 consists of a first swinging dancer arm 222 rotatably mounted to a first carriage 224 and a second swinging dancer arm 236 rotatably mounted to a second carriage 238. The first and second carriages 224,238 are slidably attached to an upper track 232 and a lower track 234. The swinging dancer arms 222,236 and carriages 224,238 operate in the manner as described above regarding the preferred embodiment above.

FIG. 12 shows this alternate embodiment of the web accumulator 220 in its maximum web storage position. When the infeed to the accumulator 220 slows or stops, the dancer arms 222,236 swing toward each other as shown in FIG. 13. When the dancer arms 222,236 rotate past some predetermined point, the first and second carriages 224,238 begin to slide towards each other as seen in FIG. 14. FIG. 15 shows this alternate embodiment of the web accumulator 220 in its least storage position.

The embodiments described above, and depicted in the FIGS. 1-15 disclose a web accumulator with a horizontal orientation. That is, the carriages slide on tracks in a horizontal direction. However, it is within the purview of the invention to utilize the web accumulator, as disclosed above, with a vertical orientation.

The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention. 

1. A web accumulator for accumulating and paying out a portion of a continuous moving web passing through the accumulator comprising: a first rotating dancer arm carrying a first plurality of rollers for engaging a moving web; a second dancer arm carrying a second plurality of rollers for engaging said web; at least one of said arms being slidably mounted to a body; a drive mechanism associated with said slidably mounted arm, wherein said slidably mounted arm can be driven in a first substantially linear direction toward the other arm, and a second substantially linear direction away from the other arm; whereby the length of travel of the web can be varied by radial movement of the first rotating dancer arm and linear movement of at least one of the dancer arms.
 2. A web accumulator according to claim 1, said first rotating dancer arm carried by a first carriage.
 3. A web accumulator according to claim 2, said second dancer arm carried by a second carriage.
 4. A web accumulator according to claim 3, said first and second carriages coupled to each other, wherein said both said first and second carriages are slidably mounted to a body.
 5. A web accumulator according to claim 4, said first and second carriages coupled by a toothed belt, wherein movement of said belt cause movement of said first and second carriages.
 6. In combination, a linear accumulator and a rotating arm dancer, wherein said rotating arm dancer and said linear accumulator operate in conjunction to first accumulate and second pay out a portion of a continuous moving web passing through the accumulator.
 7. A web accumulator for accumulating and paying out a portion of a continuous moving web passing through the accumulator comprising: a first rotating dancer arm carrying a first plurality of rollers for engaging a moving web; a second rotating dancer arm carrying a second plurality of rollers for engaging said web; at least one of said arms being slidably mounted to a body; a drive mechanism associated with said slidably mounted arm, wherein said slidably mounted arm can be driven in a first substantially linear direction toward the other arm, and a second substantially linear direction away from the other arm; whereby the length of travel of the web can be varied by linear movement of at least one of the dancer arms and radial movement of the first rotating dancer arm.
 8. A web accumulator according to claim 7 wherein the second arm is identical to the first arm.
 9. A web accumulator according to claim 8, said second arm rotated approximately 180 degrees from from said first arm when said arms are in a maximum storage position.
 10. A web accumulator according to claim 7 wherein the second arm is a mirror image of the first arm and the arms are configured such that an angle of approximately 90 degrees is formed between the arms when the arms are in a maximum storage position. 